1. Field of the Invention
This invention relates to a method for editing a PCM (pulse code modulated) signal and an apparatus for implementing this method for a case in which a feedback cross-interleaving is employed so as to record and reproduce PCM data such as an audio PCM signal.
2. Description of the Prior Art
It is well known in the art to edit an audio PCM signal series by separating the series at a predetermined number of words, adding a redundant code series for error correction, interleaving the series so as to apply different delays to the PCM data and the error correcting code series and further adding a second error detecting code.
For one of such known interleaving methods, a cross-interleaving method has been proposed in that a first redundant code is added to a PCM word series of a predetermined number of words in a first arranging mode (alignment) and a second redundant code is added to the interleaved PCM word series and first redundant code in a second arranging mode (alignment). The cross-interleaving can greatly improve the error correcting capability as compared with a simple interleaving since each word of the PCM data is included in the two series to generate the first and second redundant codes. The feedback cross-interleaving is provided to feed the second redundant code back to the first arranging mode so as to include the second redundant code in the series which generates the first redundant code and therefore, the error correcting capability is further improved.
Also, it is well known that a desired PCM signal series may be reproduced from a plurality of recording media, for example, magnetic tapes on which independent PCM signal series are recorded so as to be sequentially edited into a PCM signal series of a predetermined order. This editing procedure is performed as follows. A first desired PCM signal series is reproduced from a master tape and recorded on a slave tape or the like by a recording/reproducing apparatus. Next, the recorded PCM signal is reproduced from the slave tape and at the end portion of the first PCM signal series, a second desired PCM series reproduced from the master tape is recorded on the slave tape as the second PCM signal series by switching the recording/reproducing apparatus as described above to the recording mode. By this procedure, the desired first and second PCM signal series can be recorded on the slave tape. However, when a PCM signal series already processed by feedback cross-interleaving was reproduced for editing, it was quite difficult to perform the error correction correctly.